Gray wolves are thriving at Isle Royale National Park five years after authorities began a last-ditch attempt to prevent the species from dying out on the Lake Superior island chain, scientists said Wednesday.
Meanwhile, the park’s moose population continues a sharp but needed decline. Overpopulation of the lumbering mammals were causing their own starvation as they outstripped available balsam fir trees — their primary food during long, snowbound winters, Michigan Technological University biologists said.
The trends appear to justify federal officials’ 2018 decision to airlift mainland wolves to Isle Royale, the researchers said, arguing that the predators’ return is helping rebalance an ecosystem knocked off-kilter as their number dropped to just two.
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“We have felt and still believe that the National Park Service should not have intervened and set up this artificial population of wolves,” said Kevin Proescholdt, conservation director for the advocacy group Wilderness Watch.
A pack of wolves is seen after killing a moose at Michigan’s Isle Royale National Park. Gray wolves are thriving at the park again five years after almost dying out. (AP Photo/Rolf Peterson, Michigan Technological University)
Scientists believe the island’s first moose swam to Isle Royale around the turn of the 20th century. Wolves arrived in the late 1940s, apparently crossing the frozen lake surface from Minnesota or the Canadian province of Ontario. Though technically part of Michigan, that state’s shores are farther away.
Moose provided an ample food supply for the wolves, which in turn helped keep moose numbers in check. Both populations rose and fell over the years, influenced by disease, weather, parasites and other factors. But inbreeding finally took its toll on the wolves, whose numbers plummeted between 2011 and 2018.
Park officials and Michigan Tech scientists contend the absence of a top-of-the-food-chain predator of moose and beaver would have been ruinous for the island’s forest. Even now, its balsam firs continue to deteriorate from moose browsing and an attack of tree-killing spruce budworm, the report said.
Experts acknowledge the same factors that nearly wiped out the wolves — primarily inbreeding — eventually could return. Global warming is causing fewer ice bridges to form on Lake Superior, reducing the likelihood of wolves trekking from the mainland to the park and diversifying the gene pool. The sprawling archipelago’s closest point to the mainland is about 15 miles away.
That could mean park managers will need to import a few wolves every decade or so, Hoy said.
The moose population’s 28% drop from 2022 is one of the biggest one-year collapses ever seen at the park, it said. While wolf predation is partly responsible, necropsies indicate the biggest cause was starvation from overpopulation.
Even though relatively few moose calves appear to be surviving to adulthood, there’s no reason to worry about the moose’s immediate future, Michigan Tech biologist Rolf Peterson said. They’ve fallen to 400-500 before and bounced back. But the warming climate, tick infestations and other long-term challenges will remain.
For now, the park’s ecosystem is getting healthier thanks to the wolves’ return, he said, suggesting the decision to intervene was correct.